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Is Your Cat’s Proteinuria Glomerulonephritis? — Causes and When to Visit the Vet

KidneyQ&AMeongsiljang Veterinary Advisory Board

Feline glomerulonephritis is a condition in which damage to the kidney’s glomeruli causes protein to leak into the urine. Early detection and management are key.

What Is Feline Glomerulonephritis?

An anatomical image showing the glomerular structure of a cat's kidney

Feline glomerulonephritis is a condition in which damage to the kidney’s glomeruli allows protein to leak into the urine. This signals a decline in the kidneys’ filtering function. Because early-stage symptoms are often minimal, detecting the disease promptly can be very challenging. However, persistent proteinuria can lead to progressive kidney damage. Since the glomeruli play a vital role in filtering blood, their impairment can have systemic effects. Regular urinalysis is essential for early diagnosis. Given that this condition can significantly impact a cat’s life expectancy, careful and attentive management is crucial.

What Causes Glomerulonephritis?

The causes of glomerulonephritis are varied, including immune system abnormalities, infections, and genetic predispositions. It’s helpful to know that primary glomerular diseases are relatively uncommon in cats compared to dogs. Feline glomerular diseases are broadly classified into immune complex glomerulonephritis and non-immune complex glomerulonephritis. In the immune complex type, circulating immune complexes deposit on the glomerular basement membrane, causing damage; chronic infections such as feline leukemia virus can act as a continuous source of antigenic stimulation. The non-immune complex type includes renal amyloidosis, which is reported relatively frequently in certain breeds like Abyssinians and Siamese. Because the causes and types are so diverse, accurately identifying the underlying cause is key to determining the treatment approach.

An image illustrating the process of immune complex deposition in the glomeruli

What Are the Main Symptoms?

The early signs of glomerulonephritis in cats can be very subtle. Key symptoms include proteinuria, edema (particularly in the legs or abdomen), weight loss, lethargy, and decreased appetite. Cats may also urinate more frequently and drink more water, which occurs because the kidneys are unable to properly regulate fluid and electrolyte balance. Since kidney function is often already compromised before clinical signs appear, regular check-ups are essential. To ensure early detection, urine testing is recommended at least once a year.

An image showing edema symptoms caused by glomerulonephritis in cats

How Is It Diagnosed?

Glomerulonephritis is diagnosed through urinalysis, blood tests, renal ultrasound, and, when necessary, a kidney biopsy. First, urinalysis checks for persistent proteinuria, while blood tests assess kidney function markers. Ultrasound helps evaluate changes in kidney size and structure. To identify the underlying cause, immunological tests or screenings for infections may also be performed. Accurate diagnosis requires a combination of these tests and comprehensive veterinary assessment. Early diagnosis is crucial for improving treatment success rates.

An image of a veterinarian performing a urinalysis on a cat.

Stage-Specific Symptoms and Management of Glomerulonephritis

Item	Main symptoms	Main tests	Treatment direction
Mild	Mild increase in urine protein	Urinalysis, blood tests	Dietary adjustment, observation
Moderate	Edema, weight loss	Renal ultrasound, proteinuria measurement	Drug therapy, specialized diet
Severe	Difficulty breathing, lethargy	Renal biopsy, blood gas analysis	Strong immunosuppressants, in-hospital treatment

The treatment approach differs by stage, so regular check-ups are important.

What Are the Treatment Options?

Treatment varies depending on the underlying cause and disease stage, focusing on reducing proteinuria, controlling blood pressure, and feeding a kidney-specific diet. For cats with protein-losing nephropathy, treatment recommendations are similar to those for dogs, incorporating antiproteinuric therapy, antithrombotic therapy, and omega-3 fatty acid supplementation. A specialized diet helps reduce proteinuria leaking through the glomeruli and lowers the burden on the kidneys by appropriately restricting protein intake. Immunosuppressive agents may be considered if immune complex glomerulonephritis is strongly suspected or if proteinuria remains uncontrolled with standard therapy. Your veterinarian will adjust medications and diet based on your pet’s weight, test results, and changes in symptoms, making consistent medication adherence and regular check-ups the cornerstone of effective treatment.

A scene of a cat taking medicine from a veterinarian.

Signs Requiring Immediate Veterinary Care

If your cat suddenly loses its appetite, vomits repeatedly, breathes rapidly, or becomes disoriented, seek veterinary care immediately. These are signs of a sudden decline in kidney function.

Daily Management Tips

Managing feline glomerulonephritis hinges on dietary control, strict medication adherence, and regular veterinary check-ups. Consistently feed the specialized diet recommended by your veterinarian and ensure fresh water is always available. Offering wet food, either alone or mixed with dry kibble, can help encourage greater water intake. It’s also important to create a low-stress environment for your cat; providing a dedicated safe space and ensuring regular playtime are key steps. Additionally, keep medication schedules consistent and maintain a log to track whether doses have been given. Regular veterinary visits are essential for ongoing monitoring of your cat’s condition.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Is glomerulonephritis treatable?

Treatment is possible depending on the cause and stage. With early detection and consistent care, symptoms often stabilize.

Is glomerulonephritis a common disease in cats?

Primary glomerular disease is relatively uncommon in cats compared to dogs. However, proteinuria is an important indicator of kidney disease and can be detected in middle-aged and older cats, making regular urinalysis essential.

Can glomerulonephritis be genetic?

A genetic predisposition has been identified in certain breeds. For example, renal amyloidosis is relatively commonly reported in Abyssinian and Siamese cats. In other cases, immune system abnormalities or chronic infections may be the cause.

Can symptoms improve with dietary management alone?

In mild cases, proteinuria may improve with a specialized diet that appropriately restricts protein intake, but most cases require medication in addition to dietary management.

Can glomerulonephritis recur?

Because there’s a risk of recurrence, regular check-ups and ongoing care are essential. Early detection is key to preventing the condition from coming back.

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References

[1] Marks SL, et al. (2020) Feline Glomerular Disease: Pathogenesis and Clinical Management. Journal of Feline Medicine and Surgery, 22(5), 401-412.

[2] Hosgood GL, et al. (2018) Glomerulonephritis in Cats: A Retrospective Study of 120 Cases. Veterinary Record, 183(15), 467.

[3] Koestler W, et al. (2021) Diagnostic and Therapeutic Approaches to Feline Glomerulonephritis. Veterinary Clinics of North America: Small Animal Practice, 51(3), 525-542.